A machine tool of the type having a rotatable support for the material to be worked upon and a slide movable toward the work carrying a turret. It has been important to maintain the turret with torsional stiffness while it advances the tools carried by the turret toward the work, and this has been accomplished in some cases by using a brake to prevent rotation of the turret and with clutch means using a spring for holding the clutch surfaces in engagement such as in the patent to Samuels U.S. Pat. No. 2,975,857 which uses a brake above-mentioned as well as a spring for holding the clutch faces together. The clutch faces have been held together by springs in other patents such as U.S. Pat. Nos. De Valliere 3,161,084; Lahm 3,717,912, and Foll 3,590,673.